Color negative photographic elements are conventionally formed with superimposed red, green and blue recording layer units coated on a support. The red, green and blue recording layer units contain radiation-sensitive silver halide emulsions that form a latent image in response to red, green and blue light, respectively. Additionally, the red recording layer unit contains a cyan dye image-forming coupler, the green recording layer unit contains a magenta dye image-forming coupler, and the blue recording layer unit contains a yellow dye image-forming coupler. Following imagewise exposure, the color negative photographic elements are processed in a color developer, which contains a color developing agent that is oxidized while selectively reducing to silver latent image bearing silver halide grains. The oxidized color developing agent then reacts with the dye image-forming coupler in the vicinity of the developed grains to produce an dye image. Cyan (red-absorbing), magenta (green-absorbing) and yellow (blue-absorbing) dye images are formed in the red, green and blue recording layer units respectively. Subsequently the element is bleached (i.e., developed silver is converted back to silver halide) to eliminate neutral density attributable to developed silver and then fixed (i.e., silver halide is removed) to provide stability during subsequent room light handling.
A type of color negative processing that is widely used is the Kodak Flexicolor.TM. color negative process. Since minor adjustments of the C-41 process are undertaken from time to time, the following detailed description is provided:
______________________________________ Develop 3'15" Developer 37.8.degree. C. Bleach 4' Bleach 37.8.degree. C. Wash 3' 35.5.degree. C. Fix 4' Fixer 37.8.degree. C. Wash 3' 35.5.degree. C. Rinse 1' Rinse 37.8.degree. C. Developer Water 800.0 mL Potassium Carbonate, anhydrous 34.30 g Potassium bicarbonate 2.32 g Sodium sulfite, anhydrous 0.38 g Sodium metabisulfite 2.96 g Potassium Iodide 1.20 mg Sodium Bromide 1.31 g Diethylenetriaminepentaacetic acid 8.43 g pentasodium salt (40% soln) Hydroxylamine sulfate 2.41 g N-(4-amino-3-methylphenyl)-N-ethyl- 4.52 g 2-aminoethanol Water to make 1.0 L pH @ 26.7.degree. C. 10.00 +/- 0.05 Bleach Water 500.0 mL 1,3-Propylenediamine tetra- 37.4 g acetic acid 57% Ammonium hydroxide 70.0 mL Acetic acid 80.0 mL 2-Hydroxy-1,3-propylenediamine 0.8 g tetraacetic acid Ammonium Bromide 25.0 g Ferric nitrate nonahydrate 44.85 g Water to make 1.0 L pH 4.75 Fix Water 500.0 mL Ammonium Thiosulfate (58% solution) 214.0 g (Ethylenedinitrilo)tetraacetic acid 1.29 g disodium salt, dihydrate Sodium metabisulfite 11.0 g Sodium Hydroxide (50% solution) 4.70 g Water to make 1.0 L pH at 26.7.degree. C. 6.5 +/- 0.15 Rinse Water 900.0 mL 0.5% Aqueous p-tertiary-octyl-(.alpha.- 3.0 mL phenoxypolyethyl)alcohol Water to make 1.0 L ______________________________________
When processing is conducted as noted above, negative dye images are produced. To produce a viewable positive dye image and hence to produce a visual approximation of the hues of the subject photographed, white light is typically passed through the color negative image to expose a second color photographic element having red, green and blue recording layer units as described above, usually coated on a white reflective support. The second element is commonly referred to as a color print element, and the process of exposing the color print element through the image bearing color negative element is commonly referred to as printing. Processing of the color print element as described above produces a viewable positive image that approximates that of the subject originally photographed.
Whereas color print elements are exposed using a controlled light source, a color negative element must function under a variety of lighting conditions. When light available during exposure is marginal, increased sensitivity of the color negative elements greatly increases the opportunities for capture of pleasing and superior quality photographic images.
Color negative photographic elements that employ a single red recording emulsion layer, a single green recording emulsion layer, and a single blue recording emulsion layer are commonly referred to as "single coated". It has been long recognized that an improved speed-granularity relationship can be realized in color negative elements by dividing each of the red, green and blue recording layer units into layer units differing in speed. Color negative photographic elements having layer units divided into two layer units for recording in the same region of the spectrum are commonly referred to as "double coated". Color negative photographic elements having layer units divided into three layer units for recording in the same region of the spectrum are commonly referred to as "triple coated".
Once a light recording dye image-forming layer unit is divided into two or three layer units differing in speed for recording light in the same region of the spectrum, the opportunity is created for modifying imaging performance by varying the sequence in which the layer units are coated.
A widely used triple coated color negative photographic element layer unit sequence, Type A, is illustrated by the following triple coated layer arrangement:
Type A ______________________________________ Protective Layer Unit Fast Blue Recording Layer Unit Intermediate Blue Recording Layer Unit Slow Blue Recording Layer Unit Fast Green Recording Layer Unit Intermediate Green Recording Layer Unit Slow Green Recording Layer Unit Fast Red Recording Layer Unit Intermediate Red Recording Layer Unit Slow Red Recording Layer Unit Support ______________________________________
The Type A layer arrangement is preserved when the intermediate speed layer units are omitted to form a double coated structure. An advantage of the Type A layer sequence is that by coating all of the blue recording layer units together, all of the green recording layer units together, and all of the red recording layer units together protection against color contamination of the layer units is simplified. For example, this allows a filter layer to be interposed between the slow blue and fast green layer units to protect all of the minus blue (green or red) recording layer units from blue light exposure without reducing blue speed. It also reduces the risk of oxidized developing agent wandering from a layer unit for recording in one spectral region to a layer unit for recording in another spectral region. Typically, two interlayers containing oxidized developing agent scavenger are provided, one located between the fast red and slow green layer units and another located between the fast green and slow blue recording layer units.
The protective layer unit protects the element physically and provides a convenient location for addenda that modify physical properties. An antihalation layer unit, not shown, but almost always included, can be interposed between the slow red recording layer unit or coated on the opposite (back) side of the support. Except for dividing each of the light-recording layer units into multiple layer units, the Type A layer sequence does not differ from that of a single coated color negative element.
A common variation of the Type A layer unit sequence is the Type B layer unit sequence, commonly referred to as the "inverted magenta" layer sequence:
Type B ______________________________________ Protective Layer Unit Fast Blue Recording Layer Unit Intermediate Blue Recording Layer Unit Slow Blue Recording Layer Unit Fast Green Recording Layer Unit Fast Red Recording Layer Unit Intermediate Green Recording Layer Unit Intermediate Red Recording Layer Unit Slow Green Recording Layer Unit Slow Red Recording Layer Unit Support ______________________________________
The Type B layer arrangement is preserved when the intermediate speed layer units are omitted to form a double coated structure. In the Type B arrangement the fast, intermediate and slow red recording layer units are each coated immediately below the corresponding fast, intermediate and slow green recording layer units. This improves the red exposure record and, on balance, improves the overall performance of the color photographic element. A larger number of interlayers are employed when it is undertaken to locate oxidized color developing agent scavenger between layer units that record in different regions of the spectrum to reduce color contamination. This has not, however, precluded use of the Type B layer unit arrangement. The protective and antihalation layer units are unaffected by the inverted magenta layer unit sequence. The inverted magenta layer unit sequence was first disclosed in Eeles et al U.S. Pat. No. 4,184,876 in a double coated format.
One of the advantages of Type A and Type B layer sequences is that all of the blue recording layer units are located to receive exposing radiation prior to the minus blue recording layer units. This allows a yellow filter dye to be placed in an interlayer between the blue and minus blue recording layer units to protect the latter from color contamination caused by native blue sensitivity of the minus blue recording layer units.
Over the years many alternative layer coating sequences of layer units have been mentioned, although very few have found actual use. Research Disclosure, Vol 389, September 1996, Item 38957, XI. Layers and layer arrangements, illustrate various alternatives.
It is a customary practice to place all of the blue recording layer units farther from the support than the green and red (minus blue) recording layer units. This allows a yellow filter to be placed between the blue and minus blue recording layer units, thereby protecting the latter from blue light contamination attributable to native blue sensitivity of the silver halide grains present in the minus blue recording layer units. Kofron et al U.S. Pat. No. 4,439,520 discloses alternative layer unit sequences in which green and/or red recording layer units are coated to receive exposing radiation prior to at least one of the blue recording layer units. These arrangements are disclosed by Kofron et al to be unexpectedly free of blue light contamination of minus blue color records by the lower ratio of native blue to minus blue speed of substantially optimally sensitized high aspect ratio tabular grain emulsions.
Sowinski et al U.S. Pat. No. 5,219,715 teaches that color negative photographic elements containing tabular grain emulsions with a tabularity (T) in at least one layer unit of 50 or higher and a total imaging unit thickness of less than about 4.0 .mu.m exhibit increased sharpness and reduced color contamination. The Kodak Flexicolor.TM. color negative process described above is employed. Double coated Type A layer arrangements are disclosed.